1. Technical Field
The present disclosure relates to an organic light-emitting display device.
2. Discussion of the Related Art
With the advancement of an information-oriented society, various requirements for display devices for displaying an image are increasing. Therefore, various display devices, such as liquid crystal display (LCD) devices, plasma display panel (PDP) devices, organic light-emitting display devices, etc., are recently being used.
As a type of display device, organic light-emitting display devices are self-emitting display devices, and have better viewing angle and contrast ratio than LCD devices. Also, because the organic light-emitting display devices do not need a separate backlight, it is possible to lighten and thin the organic light-emitting display devices. Also, the organic light-emitting display devices are excellent in power consumption. Furthermore, the organic light-emitting display devices are driven with a low direct current (DC) voltage, have a fast response time, and are low in manufacturing cost.
The organic light-emitting display devices each include anode electrodes, a bank that divides the anode electrodes; a hole transporting layer, an organic light-emitting layer, and an electron transporting layer that are formed on the anode electrodes; and a cathode electrode formed on the electron transporting layer. In this case, when a high-level voltage is applied to the anode electrode and a low-level voltage is applied to the cathode electrode, a hole and an electron respectively move to the organic light-emitting layer through the hole transporting layer and the electron transporting layer, and are recombined with each other in the organic light-emitting layer to generate an exciton. Light having a particular wavelength is emitted according to energy being emitted from the generated exciton.
However, in the organic light-emitting display devices, the organic light-emitting layer is deteriorated depending on a driving duration. As such, a lifetime of the organic light-emitting layer is short. Also, in the organic light-emitting display devices, internal quantum efficiency is low, and light emitted from the organic light-emitting layer can be lost due to total internal reflection (TIR), waveguide, and a surface plasmon resonance. Also, because a polarizer for preventing reflection of external light is attached on the organic light-emitting display devices, some of the light emitted from the organic light-emitting layer can be lost by the polarizer.
Therefore, an efficient method for increasing an output of light emitted from the organic light-emitting layer is needed. As an example of an efficient method, a method in which a micro-cavity structure is applied to an organic light-emitting device is known. The term “micro-cavity” denotes that light emitted from a light-emitting layer is amplified through repetitive reflection and re-reflection between an anode electrode and a cathode electrode to cause constructive interference, and thus, emission efficiency is enhanced. In detail, in a top emission type in which light is emitted in a direction toward the cathode electrode disposed on the anode electrode, if the anode electrode is formed as a reflective electrode and the cathode electrode is formed as a semi-transmissive electrode, an output of the light emitted from the organic light-emitting layer increases using the micro-cavity structure.
FIG. 1 is a diagram illustrating a micro-cavity structure using two parallel planes according to a related art.
Anode electrodes and a cathode electrode of an organic light-emitting display device are arranged on a plane, the micro-cavity structure applied to an organic light-emitting device may be considered as a cavity structure using two parallel planes PNL1 and PNL2 as in FIG. 1. In the cavity structure using the two parallel planes PNL1 and PNL2, an irradiation direction of light L may be changed as in FIG. 1. That is, a stability of the cavity structure using the two parallel planes PNL1 and PNL2 is low. Also, in the cavity structure using the two parallel planes PNL1 and PNL2, because a cavity length varies depending on the irradiation direction of the light L (as in FIG. 1), an output light spectrum is changed depending on a light irradiation direction.